Ford Aerostar Shakes

Ok I Have Bought A Used Min Van That Is A Ford. There's Is Problem I When I Try To Speed Up The Van Shakes An Jerks Forward Until It Feel...

I Have A 96 Ford Aerostar And When I Drive Above 50 Mph It Starts To Shake And If I Go Faster It Just Gets Worse

When I Drive My Van 30 Miles Constantly The Van Will Vibrate I Took It To A Mechinac And He Repacked The Front Bearings But It Still Happens...

Especially On An Upgrade But Even While Accelerating The Van Starts To Shake Badley. Shakes Are Worse With Higher Milage. What Should I Look...